http://www.densoiridium.com/findmypart.asp

I've managed to get my hands on some of these but not sure if the ones I have are the correct ones.

Does anyone know what model no I should be using... IK16, IK20 ...etc...?

Its for an STI Version 4 Type-R...

Also, is it OK to use these...?

I use IK22 for EU MY98. May be you need IK24 use for STi engine.

thanks for the reply Erik...

I wonder what the 20, 22 etc denotes, gap(?) and if so what should it be ?

I just found out they are IK20. Can anyone confirm if these are correct...?

I hust got this info from another website:

Apparantly, Denso make the Plugs for HKS...

IK24: Thread 14mm, Reach 19mm, Heat 8, Gap 0.8mm/0.32"
IK22: Thread 14mm, Reach 19mm, Heat 7, Gap 0.8mm/0.32"
IK20: Thread 14mm, Reach 19mm, Heat 6, Gap 1.1mm/0.44"
IK16: Thread 14mm, Reach 19mm, Heat 5, Gap 1.18mm/0.44"
Heat: 8 = cold - - - 5 = warm.

Anyway, would anyone know the gap required for an STI Type-R version 4...?

...

IK20 / 22 / 24 is the heat range. Higher number is colder. Compared to NGK's ratings, 20=6, 22=7 and 24=8.

Now, I had IK22 Denso Iridiums on my MY01 STI RA for one week ONLY. The car det'ed a little now and then on WOT, but I had thought it was the fuel. On day 7, one plug blew, lighting up my knocklink momentarily and causing a minor jerk. (This is significant to me because my engine has never missed before!)

I promptly drove the short distance on 3 cyl to my mechanic. He didn't have the original NGKs in stock, so he replaced my plugs with the same Densos, but IK24. This new set never det'ed, but my faith in Denso was long gone.

As soon as I got my hands on some NGK Iridiums #8 ("IRIWAY" i think), I had them swapped out. So far so good. Only det I had was because I gave it WOT after idling for too long. 98RON fuel.

In short, if in doubt I'd go for COLDER plugs. It may cause a misfire if the carbon deposits build up too much, but at least it won't cause a cracked piston!

PS
For an STI, I'd definitely use IK24 (if you must use Densos) or NGK #8. Try their new Iridium plugs. I know that NGK do make plugs for STI (sold in STI packaging) - the "rally spec" plugs are NGK Iridiums #8.

You can check out www.japanparts.com or www.subaru-sti.co.jp to have a look at these "STI" plugs. Use a translator.

thats brilliant RT... many thanks for the info and links !!!

Anytime!

FWIW, I believe the 220hp WRX OE plug is NGK Platinium #6, and the STI comes with the same but heat #7.

So you should definitely not be going hotter than a #7 for an STI.

Heat range 7 is max for these engines whether STi or other, gap should be 0.7 (=/- 0.5) anything greater risks "blow out" of the plug. Heat range 8 will end up becoming fouled at light throttle low boost.

All cars come with heat range 6 as factory fit, heat range 7 works really well.

[Edited by Bob Rawle - 3/24/2002 3:25:58 PM]

wow
didnt know there was so much to spark plugs!

so my my99... with prodrive kit on... should i get heat 7 too?

or would heat 8 be better?
gap size?

right then...

from all your inputs, looks like NGKs platinums/iridiums heat range no 7s are the ones to go for.

Many thanks once again for all contributions!

Bob, I can't speak for the GC STI, but the plugs that came out of my standard MY01 STI RA engine are marked NGK R "PFR7G".

As I mentioned above, I'm currently on NGK "Iriway" #8. Have about 2000+kms on them, so far so good. No misfire, blow out, foul or other problems typically associated with overly cold plugs. Guess maybe the extra hot tropical weather helps with the higher engine temps?

I don't drive my car very hard, there's a lot of gear6 100kmh cruising, but I do give it a bootful now and then when the crazy traffic clears.

Standard plugs are NGK R PFR6G for STi
As Bob says 7s work better!!!!!!!!!!!!!!!!!

Darren

Up to MY96 PFR6G then up to MY00 PFR6B, if you can run 8's then you are "getting away with it" they are too cold for normal road use. Same for Eurospec (UK), WRX or STi. I gap mine at 0.68mm as that works well using HKS S35i plugs with a dia 0.4mm electrode, the Denso Iridiums are equiv to the HKS.

Darren, whats your MY and model? Is it a JDM Bugeye STI?

If not then its possible that the GC's came with #6, and the GDB's came with #7.

Bob,

Its possible NGK's and Denso's ratings don't really match up. I doubt that Denso #22 is really = NGK #7, as Denso IK22's were giving me bad det on gear3 and 4 WOT.

IK24's were fine, but as I questioned the Denso reliability, once the NGKs arrived in stock I swapped back to the #24 equivilent, which is #8. I was prepared for the possibility of some "too cold" problems, but so far so good. Will report further if anything untoward occurs. Fingers crossed!

RT, sounds as though they may be a tad "offset", det is due to using a grade too hot normally, look forward to hearing

Bob, sorry didn't understand your last post. "Look forward to hearing" ?

I agree that my det was probably due to the Denso's being too hot, altho IK22 is supposedly = NGK #7. Problem went away with subsequent plugs. The internal electrodes probably melted on my damaged plug, externally it still looked fine when we removed it.

RT ...

"Will report further if anything untoward occurs. Fingers crossed! "

Meant your further feedback NOT something untoward. Sorry for misleading.

RT.............No i drive a late 96 spec STi!!!!!!!!!!!!!!!



Darren

"Standard plugs are NGK R PFR6G for STi
As Bob says 7s work better!!!!!!!!!!!!!!!!!

Darren"

This explains our different findings then. So the GC STI came with NGK #6, and the GDB STI comes with NGK #7 as standard. Anyone find otherwise?

Can I ask the professionals which is the best replacement spark plug for a MY00 euro spec, NGK Iridium or Denso and the exactly heat range (part) number for hot climates?
Thanks in advance.
JIM

If in doubt, we tend to go for the slightly *colder* plugs in the tropics.